A man arrested over historical child sexual assaults in 2012.Source:Supplied

CHILD sex offenders are going unmonitored in the community and about 200 have gone missing from the system entirely due to a severe lack of resources, the NSW police union says.

The Police Association of NSW says there are more than 4000 offenders on the child protection register but only a fraction are monitored regularly, with the responsibility falling to stretched local police officers.

The union is calling for an urgent increase in police numbers to monitor offenders on the register and to investigate child sex offences.

“The most frightening statistic that demonstrates the complete lack of resourcing to protect our kids is that in one month only 67 of the 4000 registered offenders were intrusively monitored using the powers available to police,” union president Tony King said in a statement today.

“We need 150 more police in our commands and districts just to manage those people currently registered.”

Mr King said there were 201 offenders whose whereabouts were unknown, 80 child sex abuse cold cases that police couldn’t investigate properly, and 62 people on the register who weren’t DNA tested, “meaning that they may well be linked to current crimes but we just don’t know”.

A man arrested over historical child sexual assaults in 2012.Source:Supplied

Police Minister Troy Grant said the government had delivered consecutive record budgets for police and had added an extra 1000 officers to the force since 2011.

Police Commissioner Mick Fuller was consulting with the union on a detailed plan for the state’s future staffing needs, the minister said.

“The commissioner’s proposal will enable the government to make an informed decision on the police numbers required to meet future challenges and community needs,” Mr Grant said.

He said that “despite the fearmongering of some” the state’s crime rates had continued to fall or remain stable.